Carbon Reservoirs
A carbon atom becomes part of a tree’s trunk. In which Earth sphere is it stored?
Biosphere
A plant uses sunlight to make glucose from carbon dioxide and water. What process is occurring?
Photosynthesis
Besides carbon, name three elements that cycle through Earth’s systems.
Nitrogen, phosphorus, and oxygen. Other valid examples include hydrogen and sulfur.
A scientist draws a simplified diagram of a cycle. How can this model help explain the cycle?
It shows important reservoirs and the processes that transfer matter between them.
Water collects in a lake during its journey through the water cycle. What term describes this storage location?
A reservoir
Carbon dioxide dissolves in ocean water. Which Earth sphere receives this carbon?
Hydrosphere
An animal uses glucose for energy and releases carbon dioxide. What process returns that carbon to its surroundings?
Cellular Respiration
The atmosphere contains abundant nitrogen gas. Why can most plants still need nitrogen from the soil?
Most plants cannot use atmospheric nitrogen gas directly. They need nitrogen in usable forms.
In a model, what separates the parts counted as inside the system from those counted as outside?
The system boundary
Runoff carries dissolved phosphorus from soil into a river. How does this show that cycles interact?
Water movement transports phosphorus, connecting the water and phosphorus cycles.
A scientist finds carbon stored in carbonate rock. Which Earth sphere contains that reservoir?
Geosphere
A deer eats grass. How does this transfer carbon?
Carbon in the grass’s molecules moves into the deer through feeding.
Bacteria convert atmospheric nitrogen into forms that plants can use. What is this process called?
Nitrogen fixation.
A model includes only a lake. A stream carries water into the lake. Is this movement an input or an output? Explain.
An input, because the water crosses the boundary line
A student says a carbon atom disappears when wood burns. What actually happens to the carbon?
It becomes part of other substances, including carbon dioxide released into the atmosphere. The carbon atoms remain.
A student claims that living things contain most of Earth’s carbon. How would you correct that claim?
The geosphere contains most of Earth’s carbon, largely in rocks and sediments.
A power plant burns coal. Identify the Earth sphere the carbon leaves and the sphere it enters.
Carbon leaves the geosphere and enters the atmosphere as carbon dioxide.
Rock breaks down, releasing a nutrient into soil that plants absorb. Which cycle does this describe, and what releases the nutrient?
The phosphorus cycle. Weathering releases phosphorus from rock.
A model includes the atmosphere but excludes the ocean. Water evaporates from the ocean and enters the air. Later, rain falls into the ocean. Identify the input and output.
Evaporation supplies the input. Rain leaving the atmosphere supplies the output.
Two carbon-cycle models show different amounts of carbon in soil. Give one reason their numbers might differ.
They may use different measurements, group reservoirs differently, round values differently, or represent different times.
Why can carbon remain stored in rock much longer than it remains in a plant?
Processes that move carbon out of rock often operate over much longer timescales than processes such as respiration and decomposition.
Explain how a carbon atom in the atmosphere could enter a plant, move into an animal, and return to the atmosphere.
Photosynthesis incorporates it into the plant. Feeding transfers it to the animal. Respiration releases it as carbon dioxide.
Describe a nitrogen pathway that begins in the atmosphere, passes through living things, and returns to the atmosphere.
Fixation converts atmospheric nitrogen into usable forms. Plants absorb nitrogen, animals obtain it through feeding, and decomposition returns nitrogen to the soil. Denitrifying bacteria return nitrogen gas to the atmosphere.
One model treats the ocean as a single reservoir. Another separates surface water from deep water. Why might both models be useful?
They serve different purposes. The simpler model shows overall transfers, while the detailed model shows differences between surface and deep water.
Your cycle model shows where matter moves but does not show how quickly it moves. Identify this limitation and explain what you would add.
The model cannot show transfer rates or how quickly reservoirs change. Add information about the amount of matter transferred over time.